[Rd] interaction.plot

From: Christoph Buser <buser_at_stat.math.ethz.ch>
Date: Fri 06 Aug 2004 - 18:24:40 EST

Dear R core team

I've a proprosal to improve the function interaction.plot. It should be allowed to use type = "b". This can be done by changing the function's header from

function( , type = c("l", "p"), )


function( , type = c("l", "p", "b"), )

Then it works. This type = "b" is useful, if the second level of the x.factor is missing for some level of the trace.factor. With type= "l" you loose first level of the x.factor, too (because you can't draw the line to the missing second level). With type = "p" so see this first level, but you have no lines at all (just chaos with points). With type = "b", you get all existing levels plus the lines between two contiguous levels (if they both exist).

There is a second point. Using interaction.plot with the additional argument main creates a warning:

parameter "main" couldn't be set in high-level plot() function

The reason is that "..." is used twice inside of interaction.plot, in fact in

matplot( ,...)

and in

axis( ,...)

axis can do nothing with this argument main and creates this warning. You could replace ,... in the axis function by inserting all reasonable arguments of axis in the functions header (interaction.plot) and give over those arguments to axis. Then you shouldn't get this warning anymore.

Best regards

Christoph Buser

Christoph Buser <buser@stat.math.ethz.ch>
Seminar fuer Statistik, LEO D6
ETH (Federal Inst. Technology)	8092 Zurich	 SWITZERLAND
phone: x-41-1-632-3505		fax: 632-1228

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Received on Fri Aug 06 19:43:21 2004

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